This invention relates to glycol-based compositions useful as antifreeze fluids in heat-transfer applications or as deicing fluids for aircraft.
Glycol-based fluids are commonly employed as in heat-transfer fluids and as deicing fluids for aircraft. The formulations are typically based on alkylene glycols such as ethylene and propylene glycol. Since it is known that metal surfaces sometimes corrode when contacted with fluids of water and glycol, a wide assortment of corrosion inhibitors are often added to alleviate this side effect. A problem exists, however, because when water is used to dilute concentrated glycol-based fluids, cations such as calcium and magnesium ions from the water form precipitates with various anions from additives to the glycol-based fluid. When this happens, the diluted mixture becomes turbid. This effect is undesirable and both the United States and Canada will soon require aircraft deicing fluids to remain clear on contact with water.
Aircraft deicing fluids are known which incorporate viscous homopolymers and copolymers of acrylic acid, methacrylic acid, or maleic acid, or cross-linked polymers thereof, to thicken the fluids. The thickened fluids coat the aircraft and, thus, prevent the buildup of ice. Such compositions are disclosed, for example, in U.S. Pat. Nos. 3,940,356: 4,358,389: and 4,744,913.
It can be seen that the prior art lacks a way of preventing the precipitation of salts from glycol-based compositions when the compositions are admixed with water, especially hard water. A solution to this problem would be of benefit to the public as well as to the users and manufacturers of these glycol-based fluids.